Traditionally, in order to reduce the thickness of displays such as liquid crystal based displays, signs, and backlights, edge-lit configurations using rigid lightguides have been used to receive light from the edge and direct it out of a larger area face. These types of light emitting devices are typically housed in relatively thick, rigid frames that do not allow for component or device flexibility and require long lead times for design changes. The volume of these devices remains large and often includes thick or large frames or bezels around the device. The thick lightguides (typically 2 mm and larger) limit the design configurations, production methods, and illumination modes.
The ability to further reduce the thickness and overall volume of these area light emitting devices has been limited by the ability to couple sufficient light flux into a thinner lightguide. Typical LED light sources have a light emitting area dimension of at least 1 mm, and there is often difficulty controlling the light entering, propagating through, and coupled out of a 2 mm lightguide to meet design requirements. The displays incorporating the 2 mm lightguides are typically limited to small displays such as those with a 33 cm diagonal or less. Many system sizes are thick due to designs that use large light sources and large input coupling optics or methods. Some systems using one lightguide per pixel (such as fiber optic based systems) require a large volume and have low alignment tolerances. In production, thin lightguides have been limited to coatings on rigid wafers for integrated optical components.